chore(backend): migrate Prisma to v7 with prisma.config and direct migration URL

[BODMAT]

This PR upgrades backend Prisma integration to v7 and aligns configuration with the new Prisma 7 approach.

What changed

• upgraded prisma and @prisma/client to v7
• added @prisma/adapter-pg and pg
• introduced apps/backend/prisma.config.ts
• moved datasource URL handling out of schema.prisma
• switched runtime Prisma client initialization to adapter-based connection (PrismaPg) in:
  • apps/backend/src/prisma.ts
  • apps/backend/prisma/seed.ts
• added DIRECT_URL to backend env example for migration/direct DB connection
• updated backend package configuration accordingly
• normalized repo line endings and Prettier EOL policy

CI / test setup

• exposed DIRECT_URL / DATABASE_URL to CI at the job level in .github/workflows/ci.yml so all steps (lint/build/tests) inherit them
• removed the duplicate explicit prisma generate CI step — backend build script already runs it
• declared DIRECT_URL / DATABASE_URL as globalPassThroughEnv in turbo.json so Turbo forwards them to tasks (Turbo otherwise strips env vars from task environments)
• adapted Jest globalSetup to Prisma 7:
  • dropped the now-removed --skip-generate flag from prisma db push
  • set DIRECT_URL alongside DATABASE_URL for the testcontainers Postgres instance, since prisma.config.ts reads DIRECT_URL

Why

• Prisma 7 deprecates/removes old datasource URL usage in schema-based workflow
• this setup separates:
  • runtime pooled connection (DATABASE_URL)
  • migration/direct connection (DIRECT_URL)
• reduces deploy issues with pgBouncer/pooler setups (e.g. Supabase + Render)

Notes

• DATABASE_URL should point to pooled/runtime endpoint
• DIRECT_URL should point to direct DB endpoint (typically :5432 + SSL)
• no functional business-logic changes are intended in this PR